1. Field of the Invention
Embodiments of the present invention generally relate to wireless communication systems, and more particularly to wireless personal area networking and wireless local area networking.
2. Description of the Related Art
Wireless communication systems transfer data from a transmitting station to one or more receiving stations using modulated radio frequency (RF) signals. Bluetooth™ systems are wireless communication systems governed, in part, by the Bluetooth™ Special Interest Group (SIG) which publishes specifications and compliance standards. The current Bluetooth™ standards, up to version 2.1, are designed for low power consumption, short range communication at rates of 1 to 3 Mbps. The next generation of Bluetooth™ standards, still in development, proposes using radio transmission methods capable of significantly higher data rates. To maintain the low power methods of current Bluetooth™ standards, an alternative physical layer radio may be used for high rate data transmission when required, while the low power Bluetooth™ radio may be used otherwise. The IEEE 802.11 wireless local area networking standards provide exemplary higher data rate transmission methods using the same radio frequency band as Bluetooth™ standards, and the Bluetooth™ SIG has proposed adopting some of the IEEE 802.11 wireless standards as alternate physical layers for the next generation Bluetooth™ standard.
Both the Bluetooth™ and IEEE 802.11 wireless standards use the unlicensed industrial scientific medical (ISM) frequency band from 2.4 GHz to 2.4835 GHz including guard bands at the upper and lower boundaries. Bluetooth™ physical layer radio channels may frequency hop among a set of 79 different 1 MHz wide radio frequency channels, while an IEEE 802.11 physical layer radio channel may occupy a 20 MHz or 40 MHz contiguous frequency band. A first set of devices using Bluetooth™ standards and a second set of devices using an IEEE 802.11 wireless standard within the same physical range may likely interfere with one another. Some prior art has focused on applying time division multiplexing and frequency division multiplexing techniques to the different sets of devices to mitigate interference in a wireless network using both standards. Increasingly, however, portable electronic devices such as laptop computers, personal digital assistants and cellular telephones may incorporate hardware to support multiple wireless standards in the same device, with multiple standards to be used simultaneously.
A set of Bluetooth™ devices that form a piconet may communicate by frequency hopping in a pseudo-random manner among a set of 79 different frequencies in the ISM band. Several of these frequencies may overlap with a frequency band used by a collocated IEEE 802.11 wireless local area network (WLAN). The Bluetooth™ standard specifies an adaptive frequency hopping technique that may minimize the frequency overlap and thereby the interference between the Bluetooth™ piconet devices and the IEEE 802.11 WLAN devices; however, a Bluetooth™ transceiver and an IEEE 802.11 WLAN transceiver collocated in the same device may still interfere with one another. For example the transmit spectrum of an IEEE 802.11 WLAN transmitter may be relatively strong measured at a collocated Bluetooth™ receiver so as to mask the presence of a relatively weak Bluetooth™ receive spectrum even if the spectra do not directly overlap. Smaller portable devices may place an IEEE 802.11 WLAN transmitter and a Bluetooth™ receiver relatively close together physically and may exhibit such interference. A system using non-overlapping but interfering spectra may still use time division techniques to minimize interference.
FIG. 1 illustrates a prior art dual protocol Bluetooth™/802.11 device 100 that may communicate with a Bluetooth™ device 110, thereby forming a Bluetooth™ personal area network (PAN) 130, as well as an IEEE 802.11 device 120, thereby forming an IEEE 802.11 local area network (LAN) 140. Bluetooth™ and IEEE 802.11 higher layers may communicate with each other in the Bluetooth™/802.11 device 100 to reduce interference; however, a Bluetooth™ protocol stack may be restricted to using the lower rate Bluetooth™ physical layer radio to communicate with the Bluetooth™ device 110, even though the Bluetooth™/802.11 device 100 also contains a higher rate IEEE 802.11 physical layer radio.
FIG. 2 illustrates a dual physical layer Bluetooth™ device 200, where, as proposed for the next generation Bluetooth™ standard, a device may use both a Bluetooth™ physical layer radio and an IEEE 802.11 physical layer radio to enable a higher data rate Bluetooth™ connection. The Bluetooth™ physical layer radio may be used for lower speed operations, such as device discovery, initial connection, profile configuration, and low speed data transfer. The IEEE 802.11 physical layer radio may be used selectively for higher speed data transfer. If the dual physical layer Bluetooth™ device 200 is a master device that controls the data flow in a Bluetooth™ network and the Bluetooth™ device 210 is a slave device, then the dual radio Bluetooth™ master device 200 can alternate between using a Bluetooth™ physical layer radio and an IEEE 802.11 physical layer radio as required; however, the dual radio Bluetooth™ slave device 210 cannot initiate use of its IEEE 802.11 physical layer radio according to currently proposed Bluetooth™ standards.
Thus, there exists a need for a multiple radio transmission method within the same device that may provide an efficient, shared use of the same frequency band, overlapping frequency bands or adjacent frequency bands within a wireless communication system.